A concave type structure has been conventionally employed for the capacitor structure in a dynamic random access memory (DRAM). In this structure, a lower electrode film is formed inside a cylinder bore, and only the inner surface is made to function as an electrode. According to this structure, the area occupied by the capacitor can be certainly made small. The diameter of the cylinder bore is however necessarily decreased. Besides, it is necessary to secure the capacitance needed for the device operation of the DRAM. In order to satisfy these two requirements, the depth of the cylinder bore is further deepened. As such, that would make more difficult appropriately to cope with the production of capacitors in terms of microprocessing technology.
Attempts have been made to control the aspect ratio of the capacitor structure, but the process per se is not so simple as to forming a fine cylinder structure or a bore therein with high accuracy. Usually, this process is carried out by wet etching. That is, in order to leave a tubular structure having a cylinder wall with a nanometer to submicrometer size with a certain depth in a semiconductor substrate, the material inside and outside the tubular structure should be removed using an etching liquid. In particular, removal of the material inside the cylinder bore or between the cylinder structures must be done in a manner such that the material is scraped out of an enclosed space. The removal of material hence involves difficulties in a processing carried out by wet etching.